Programmed-cell-death events in the tapetum of two angiosperms (Lobivia rau
schii Zecher and Tillandsia albida Mez et Purpus) are described by ultrastr
uctural methods. Tapetum degradation appears to be a type of programmed cel
l death, with the cellular remnants necessary for pollen development, actin
g as products of holocrine secretion. Diagnostic features of apoptosis duri
ng tapetum development are: general shrinkage of the whole cell and the nuc
lei; condensation of the chromatin at the periphery of the internal nuclear
membrane; the enlargement of the endoplasmic-reticulum cisternae to circum
scribe portions of the cytoplasm; the persistence of mitochondria together
with microfilament bundles until the last stages of tapetal degeneration.